The present invention relates to a liquid crystal display device and, more particularly, to an active matrix type liquid crystal display device which functions at least as a reflection type display device.
In an active matrix type liquid crystal display device, on a liquid-crystal-side surface of one of a pair of substrates which are arranged to face each other with a liquid crystal disposed therebetween, regions which are surrounded by gate signal lines extending in the x direction and arranged in the y direction in parallel and drain signal lines extending in the y direction and arranged in the x direction in parallel are formed as pixel regions. A thin film transistor, which is driven by scanning signals (voltage) from a one-sided gate signal line, and a pixel electrode, to which video signals (voltage) are supplied from a one-side drain signal line through the thin film transistor, are provided in each pixel region. The pixel electrode generates an electric field between the pixel electrode and a counter electrode which is formed on the other-substrate side in common with each pixel region so as to control the light transmittivity of the liquid crystal material disposed therebetween.
There is a known liquid crystal display device in which a portion or the whole of each pixel electrode is formed of a metal layer having a high light reflectance. This type of liquid crystal display device functions as a reflection type display device. Since such a liquid crystal display device enables a viewer to recognize images by making use of external light, such as sun light, the power consumption of the device can be reduced. However, so long as a liquid crystal display device is operated to function as a reflection type device, there arises a problem in that a sufficient external light cannot be ensured for every site where the liquid crystal display device is to be used. Accordingly, a device construction which can enhance the numerical aperture becomes more important in this type of display device compared to other kinds of liquid crystal display devices.
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a liquid crystal display device having a constitution which can enhance the numerical aperture.
Further, it is another object of the present invention to provide a liquid crystal display device which can eliminate the light reflection derived from signal lines.
It is still another object of the present invention to provide a liquid crystal display device which can prevent the leaking of light from a backlight when the liquid crystal display device is constituted as a partial reflection type (provided with a backlight).
The summary of typical examples of various aspects of the invention disclosed herein will be outlined below.
That is, a liquid crystal display device according to the present invention includes, for example, a plurality of gate signal lines which are formed on an insulation substrate, a plurality of drain signal lines which are formed on the insulation substrate such that the drain signal lines intersect the gate signal lines, thin film transistors which are connected to the gate signal lines, the drain signal lines and reflection electrodes which are connected to the thin film transistors, the thin film transistors and the reflection electrodes being formed on pixel regions which are surrounded by these respective signal lines, and sequential laminated bodies, each of which is made of at least a light shielding film and a semiconductor layer, each sequential laminated body being formed between the reflection electrode and the reflection electrode of another neighboring pixel region such that the sequential laminated body is superposed on the sides of these reflection electrodes.
In the liquid crystal display device having such a constitution, the light shielding film is formed between the reflection electrodes of respective pixel regions, and, hence, it is no longer necessary to provide a black matrix, which has a function similar to the function of the light shielding film, on the other insulation substrate.
This implies that it becomes possible to narrow the width of the light shielding films without taking the tolerance of superposition between one insulation substrate and the other insulation substrate into consideration, whereby the numerical aperture can be enhanced.
Further, the semiconductor layers are formed over the light shielding films, and, hence, the reflection of an external light on the light shielding films can be largely reduced.